Textures stretching when UV mapping
First, in Object Mode, check that the object isn't scaled on any axis - scale should be '1.000' for x, y and z as in the screenshot below. If you have numbers other than 1 you can fix this by going to Object &gt; Apply &gt; Scale in the top left of the 3d viewport.

If that's fine you can try re-unwrapping the object by selecting all the faces in Edit Mode, pressing U key and selecting Smart UV Project. If the texture still looks wrong, select the faces individually in edit mode in the 3D Viewport then select the corresponding face in the UV Editing window and rotate and scale it until you get the right look.
Good luck!